1. Field of Invention
The present invention relates to a system and a method for determining the position and/or orientation, particularly the direction of vision, of an eye by the serial intercepting of a beam reflected by a part of the eye.
2. State of the Art
The knowledge of the momentary orientation of an eye is a necessary prerequisite for a plurality of the most different applications:
In medicine, the treatment of defective vision, retinal detachments, macula degeneration, etc. requires the detection of voluntary and mainly involuntary orientation changes of the eye in order to, for example, be able to appropriately cause a laser beam to follow in such a manner that, in each case, it impinges on the same point on the retina or moves along a certain trajectory on the retina.
In psychology, the orientation of the eye permits diverse conclusions. Thus, for example, a sudden strong rotation indicates the beginning of a grand mal or a black-out. Furthermore, significantly more extensive information can be obtained from the direction of vision of the eye, which can be determined, for example, by the mean perpendicular of the pupil. As an example, the recognition pattern of test persons when viewing certain pictures can be analyzed in this manner.
In addition, the knowledge of the direction of vision offers the possibility of using the information that indicates where the viewer is momentarily looking in order to identify the fixed object; whether it is a certain menu item on a (virtual) video screen, a device to be activated (light switch, etc.), a selected target of a rocket launcher, or the like.
Furthermore, the knowledge of the orientation and particularly of the direction of vision of the eye makes it possible to, for example, project visual information into the eye, which information is correlated with the viewer's perceived picture of the environment or his virtual orientation (for example, when using virtual-reality spectacles or the like), so that the pictures projected into the eye, for example, are seemingly resting in space or relative to an object, or the merged picture changes corresponding to the direction of the vision of the user of the virtual-reality spectacles.
Diverse devices and methods have therefore been developed for detecting the orientation of the eye:
German Patent Document DE 196 31 414 A1 mentions sensors which are fixed directly to the eyeball. These naturally, on the one hand, represent a considerable danger to and impairment of the test person, and, on the other hand, can also not detect the direction of vision of the eye (for example, in the case of strabismic persons) and, in addition, are quite inaccurate relative to the often minimal involuntary movements of the eye.
Furthermore, the integral taking of the retina reflex picture by CCD cameras is mentioned, which, on the one hand, because of the high exposure, is suitable for the low-light reflex picture but, on the other hand, comprises a very large quantity of data resulting in low processing speeds as well as distortion problems.
The above-mentioned document therefore suggests a device where an image of the environment reflected by the retina is serially scanned by means of a scanning device, is electronically modified and subsequently is projected back into the eye.
However, in this case, the orientation of the eye, particularly the direction of vision, is not determined but only a reflected and subsequently processed image of the environment is projected back into an eye on the same beam path in order to ensure a superimposing with the actually perceived image.
In the still unpublished Application PCT/EP01/05886, many different methods and devices are also described for the adaptation of an optical system to the direction of vision of the human eye.
It is therefore an object of the present invention to provide a device and a method by means of which the position and/or the orientation, particularly the direction of vision, of an eye can be determined rapidly and precisely.